Ebullated bed process for high conversion of heavy hydrocarbons with a low sediment yield

Abstract

An ebullated bed process for the hydroconversion of heavy hydrocarbon feedstocks that provides for high conversion of the heavy hydrocarbon with a low sediment yield. The process uses for its catalyst bed an impregnated shaped ebullated bed catalyst having a low macroporosity and a geometry such that its characteristic cross section perimeter-to-cross sectional area is within a specifically defined range.

Claims

1. A process that uses an ebullated bed reactor system for the hydroconversion of a heavy hydrocarbon feedstock, having a high proportion of pitch hydrocarbons boiling at temperatures exceeding 524 C., to yield a heavy hydrocarbon conversion product having a low sediment content, wherein said process comprises: introducing said heavy hydrocarbon feedstock, having a content of said pitch exceeding 50 wt.%, into an ebullated bed reaction zone contained within a reactor volume defined by an ebullated bed reactor vessel, wherein said reactor volume includes an upper zone above said ebullated bed reaction zone and a lower zone below said ebullated bed reaction zone, wherein said ebullated bed reaction zone comprises a catalyst bed of small particle size, shaped hydroprocessing catalyst particles, wherein said shaped hydroprocessing catalyst particles comprise a calcined shaped alumina support, which consists essentially of alumina, wherein the alumina is calcined at a first temperature to form the calcined shaped alumina support, wherein the calcined shaped alumina support is impregnated with at least one active catalytic metal component followed by calcination at a second temperature providing said shaped hydroprocessing catalyst particles, and wherein said shaped hydroprocessing catalyst particles are further characterized as having a low macroporosity in the range of from greater than 0.01% to less than 9% and a geometry defined by a length and a polylobal cross section providing for a first ratio of the cross section perimeter-to-cross sectional area that is in the range of from 5 mm.sup.1 to 8 mm.sup.1; contacting under hydroconversion reaction conditions said heavy hydrocarbon feedstock with said shaped hydroprocessing catalyst particles within said ebullated bed reaction zone; and yielding from said upper zone said heavy hydrocarbon conversion product having less than 0.5 wt.% sediment, as determined by testing method ASTM-4870.

2. A process as recited in claim 1, wherein said shaped hydroprocessing catalyst particles further include an amount of inorganic oxide component in the range of from about 70 wt.% to 99 wt.%, a molybdenum compound in an amount in the range of from 3 wt.% to 15 wt.%, and a nickel compound in an amount in the range of from 0.5 wt.% to 6 wt.%, wherein each wt.% is based on the total weight of said shaped hydroprocessing catalyst particle and the metal as an oxide regardless of its actual form.

3. A process as recited in claim 2, wherein said hydroconversion reaction conditions include a contacting temperature in the range of from 316 C. (600 F.) to 538 C. (1000 F.), a contacting pressure in the range of from 500 psia to 6,000 psia, a hydrogen-to-oil ratio in the range of from 500 scf/bbl to 10,000 scf/bbl, and liquid hourly space velocity (LHSV) in the range of from 0.1 hr-1 to 5 hr-1.

4. A process as recited in claim 3, wherein said polylobal cross section is a trilobal cross section.

5. A process as recited in claim 4, wherein said cross section perimeter-to-cross sectional area that is in the range of from 5.5 mm.sup.1 to 7 mm.sup.1.

6. A process as recited in claim 5, wherein said low macroporosity is greater than 0.1% and less than 6% of the total pore volume of pores having a diameter greater than 350 contained in said shaped hydroprocessing catalyst particles.

7. A process as recite in claim 5, wherein said low macroporosity is greater than 0.35% and less than 2% of the total pore volume of pores having a diameter greater than 350 contained in said shaped hydroprocessing catalyst particles.

8. The process as recited in claim 1, wherein the second temperature is different from the first temperature.

9. The process as recited in claim 1, wherein the second temperature is lower than the first temperature.

Description

EXAMPLE 1

(1) This Example 1 describes the preparation of a large particle, impregnated comparison Catalyst A, having a geometry such that the value for its characteristic cross section perimeter-to-cross sectional area is small and that of a small particle, impregnated Catalyst B having use in one embodiment of the invention and a geometry such that the value for its characteristic cross section perimeter-to-cross sectional area is relatively large.

(2) An extrudable alumina paste or mixture was prepared by combining 200 parts of alumina powder, 1 part of nitric acid, and 233 parts of water. A portion of the mixture was then extruded through cylindrical extrusion holes and a portion of the mixture was extruded through trilobe extrusion holes. The extrudates were dried at 121 C. (250 F.) for 4 hours in an oven and then calcined at 677 C. (1250 F.) for an hour in a static furnace. The resulting alumina supports (comprising, consisting essentially of, or consisting of alumina) were then impregnated with a portion of an aqueous solution containing molybdenum, nickel and phosphorus, in amounts so as to provide catalysts with the metal loadings indicated in Table 1, dried at 121 C. (250 F.) for 4 hours, and calcined at 482 C. (900 F.) for an hour.

(3) Selected properties for the resulting Catalyst A and Catalyst B are summarized in Table 1. It is noted that these catalysts contain insignificant macroporosity.

(4) TABLE-US-00002 TABLE 1 Catalyst A Catalyst B Pellet diameter, mm 0.93 0.97 Pellet shape Cylinder Trilobe Average pellet length, mm 3 3 Pellet cross section perimeter/area 4.35 7.73 Pellet surface/volume 5.01 8.40 Total PV, cc/g 0.73 0.73 MPD, A 105 105 Vol > 350 A, cc/g 0.02 0.02 Mo, wt % 6.5 6.5 Ni, wt % 1.8 1.8 P, wt % 0.7 0.7

EXAMPLE 2

(5) This Example 2 describes the conditions of the performance testing of Catalyst A and Catalyst B and the results of the performance testing.

(6) The catalysts were tested in a 2-stage CSTR pilot plant. The properties of the feed are summarized in Table 2, and the process conditions are presented in Table 3.

(7) TABLE-US-00003 TABLE 2 Properties of the feed used to evaluate the catalysts 1000 F.+, wt % 87.7 SULFUR, wt % 5.255 MCR, wt % 20.8 NICKEL, wppm 43 VANDIUM, wppm 130 FEED DENSITY, g/ml 1.0347 n-C7 Insolubles, wt % 12.7 n-C5 Insolubles, wt % 20.9

(8) TABLE-US-00004 TABLE 3 Processes conditions used to evaluate the catalysts Catalyst LHSV, hr.sup.1 0.55 Total pressure, psia 2250 H2/Oil ratio, scft/bbl 4090 Temperature, F. 795

(9) The performance of Catalyst B relative to the performance of Catalyst A (Base) summarized in Table 4.

(10) TABLE-US-00005 TABLE 4 Relative performance of the catalysts Catalyst Catalyst A Catalyst B 1000 F. conversion, wt % Base 100 Relative 650 F..sup.+ Sediments, % of Base 64 base Relative 650 F.+ Sulfur, % of base Base 101 Relative 650 F.+ density, % of base Base 100

(11) A review of the performance results presented in Table 4 show that the conversion and desulfurization catalytic performance of Catalyst B are essentially the same as those of Catalyst A. Catalyst B, however, unexpectedly provides for a huge improvement in sediment yield as compared to Catalyst A. Catalyst B unexpectedly provides for 64% of the sediment yield that is provided by Catalyst A; thus, giving a 36% reduction in sediment yield over that provided by Catalyst A. These results show that, the impregnated and low macroporosity ebullated bed catalyst particles, having a small particle size and specific geometry (i.e., cross section perimeter-to-cross sectional area ratio), unexpectedly affects sediment yield while having little or no impact on other of the catalytic properties, such as, conversion and desulfurization.